QUESTION 1:- (a) A 4-pole, 3-phase, star-connected, 50 Hz synchronous generator, with a synchronous impedance of j24.5 Ω/phase and negligible resistance, delivers 5 MW of power to a 13.8 kV busbar. At this operating point, the excitation is equal to 1.8 p.u. Calculate the phase value of the generated emf (E) and hence calculate the electrical load angle, δ, at which the machine is operating.
QUESTION 1:-
(a) A 4-pole, 3-phase, star-connected, 50 Hz synchronous generator, with a synchronous impedance of j24.5 Ω/phase and negligible resistance, delivers 5 MW of power to a 13.8 kV busbar. At this operating point, the excitation is equal to 1.8 p.u. Calculate the phase value of the generated emf (E) and hence calculate the electrical load angle, δ, at which the machine is operating.
(b) Sketch a typical operating chart for a salient pole synchronous generator and on the chart identify the following;
- The Apparent Power limit,
- The field (excitation) limit,
- The Real Power limit,
- A line which represents a constant lagging power factor, The rotor angle for operation at any given point of operation, e.g.
- rated power and 0.9 power factor lag.
(c) A Stamford HCI534F framesize generator has been selected for a stand-alone diesel-generation application. The generator is to operate at 400 V, 50 Hz, with the self-excited (SX) excitation scheme. Datasheet information can be found in Appendix 1.
- If a load of 268 kVA, 0.8 lag power factor is applied to the generator, determine the efficiency at which it will operate and hence calculate the engine size required, in kW.
- A 400 V, 50 Hz, 57 kW motor is to be started DOL from the generator. The motor’s efficiency is 90.3% and its running power factor is 0.85 lag. Determine what % transient voltage-dip will be experienced by the generator as the motor starts.
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